So the key thing is - don't try to model that curved cup piece only directly to the cross outline, that would be difficult to form very well as one big smooth piece.

Instead you want to make a broader extended curved surface for the cup portion, and you introduce the cross outline by doing a boolean using that broad surface so that the surface gets cut by that cross boundary.

Often times it is much easier to build a curved object when you initially ignore any irregular boundaries on the outside and instead just build an initially larger and more extended and simple piece.

This overall concept of modeling extended surfaces and then using booleans to introduce the final edges by removing material can take a while to get comfortable with, especially if you're coming from a polygon modeling background since it's a very different process from polygon modeling.